In pouch or bag-shaped beverage containers having a membrane seal which is to be pierced by a pointed straw, there is a problem making the seal sufficiently easy for the consumer to pierce with a straw. The piercing of the membrane seal may be an especial problem for small children who frequently utilize such containers and who lack the dexterity of adults.
In one prior art opening system a simple membrane seal has been used on an inside surface of one barrier wall of a bag-shaped container. The membrane seal is sealed up to the edges of the straw hole in the barrier wall near a top of the container. The membrane is flush with the inner surface of the barrier wall and the membrane area covering the straw hole is essentially unyielding. Such a membrane seal is disclosed in U.S. Pat. No. 5,425,583 (Wild). While such a membrane seal is an improvement of present commercial opening systems it is often difficult for young children (ages 4-9) to use since the membrane must be struck with the straw only in the hole in the barrier wall and at the same time with somewhat of a downward angle so that the straw does not pierce as well the back barrier wall of the container. In addition, once (and as) the membrane is pierced, the membrane is torn and squeezing of the bag-shaped container may result in the beverage being pushed up around the outside of the straw and out of the straw hole causing undesired spillage.
Another opening system using two distinct membrane seals for a bag-shaped container is disclosed in U.S. Pat. No. 4,553,693 (Terajima et al.). A first membrane seal is attached on the inside surface of the barrier wall about the straw hole and to a tamper-evident, pealable tab attached to an outer surface of the barrier wall. Covering the first membrane and attached to the inside surface about the first membrane is a second membrane which is at least partially pierced. When the tab is peeled from the barrier wall, the part of the first membrane covering the straw hole is also pealed away therewith. This exposes the second membrane which is easily pierced by the straw, as it is already at least partially pierced. However, such opening systems are complex and expensive.